Traditionally, the indicia of license plates for motor vehicles have been incorporated into the plate by painting, stamping, embossing or the like. The starting product in the manufacture of license plates is customarily a plate or sheet blank of suitable thickness. This plate or sheet blank is typically made of metal, e.g., aluminum, or, more recently, of a suitable plastic material, e.g., acrylonitrile-butadiene-styrene ("ABS") copolymers, and is usually stamped or molded with a thickened rim or edge portion to provide greater rigidity. The plate manufacturer typically forms the desired indicia or markings by stamping the rear face of the blank so that the . indicia appear on the front face thereof in embossed fashion. The indicia, which are raised in relief relative to the background, are then typically colored with a different color than that of the background, such as by applying a colored coating to the raised area, e.g,. by rollers.
Many countries use light reflecting, preferably retroreflective, license plates in order to improve recognition and reading of the identifying indicia, i.e., numerals and/or letters, on the plates at nighttime, and to increase traffic safety. When manufacturing such plates, a reflective material or substance is typically applied to the plate blank before the indicia are embossed therein. After embossing, the raised areas which constitute the indicia are covered or coated to provide contrast with the background. At nighttime and upon reflection, the coated indicia appear black whereas the reflective background, by contrast, appears bright and light-colored. The indicia coating is preferably chosen to provide daytime color contrast with the typically light-colored or white background.
It has been proposed that instead of coating raised areas with a colored coating material, that reflective material, such as retroreflective sheeting, be selectively applied only in the background areas of the plate around the raised indicia, with the indicia being provided by the exposed raised plate material. While such a technique avoids the previous practice of coating the raised areas of the plate with a special durable colored coating material, it has several difficulties. For example, selective application requires accurate trimming or prepunching of the reflective sheeting to conform to the indicia, and accurate placement of the trimmed reflective sheeting in alignment with the indicia. Since the sheeting typically comprises a pressure-sensitive adhesive and is difficult to move after contacting the plate, accurate initial placement is demanded.